Studies will be carried out on the effect of physiologic plasma concentrations of catecholamines on heart rate, A-V conduction, and ventricular contractility in normal and failing hearts under controlled hemodynamic conditions. To be examined is the mode of utilization of catecholamines in the failing heart and the possibility of myocardial supersensitivity to norepinephrine in congestive heart failure. The results of this study, combined with previously accumulated data on catecholamine release in congestive heart failure, should allow an estimate of the importance of the humoral portion of the adrenergic system in supporting the failing heart.